1. Field of the Invention
This invention relates to a zero load insertion type socket for an electric part including a means for displacing a contact between a contacted position and a released position.
2. Brief Description of the Prior Art
In a conventional socket represented by, for example, U.S. Pat. No. 4,623,208, a contact itself includes a cantilevered arm projecting outwardly. When the cantilevered arm is pushed down with a presser cover, a curved spring portion, which is provided as part of the contact itself, is flexed in the compressing direction to realize an outward displacement to thereby separate a contact nose portion from a contact of an IC, so that the IC can be inserted and removed with no load.
In the above-mentioned conventional IC socket, the operational force for pushing down the presser cover and the contacting force of the contact are determined by the spring portion of the contact.
Accordingly, if a spring constant of the spring portion is increased in order to increase the contacting force, the operational force necessary for pushing down the presser cover must also be increased. On the contrary, if the spring constant of the spring portion is reduced in order to reduce the necessary operational force, the contacting force is also reduced. The conventional IC socket incurred these problems. Therefore, it was difficult for the conventional IC socket to be designed so as to satisfy both the requirement of reducing the operational force as much as possible and increasing the contacting force.
The arrangement in which the spring portion must be compressed in order to obtain an outward displacement motion by pushing down the cantilevered ar is inconvenient in that the amount of outward displacement realized relative to the amount by which the cantilevered arm is pushed down is very limited, and in that an efficient amount of displacement relative to the amount by which the cantilevered arm is pushed down is unobtainable.
It is also undesirable that when the cantilevered arm is pushed down, the axis of the contact tends to be twisted, an undesirable shifting of the contact nose portion occurs, and metal fatigue tends to accumulate in the basal portion of the cantilevered arm when an external force is repeatedly exerted on the cantilevered arm in the curved direction.
In the conventional contact, various complicated design specifications or conditions must be satisfied, such as providing a sectional area which will provide a certain strength, and setting of the spring constant, and a counter-measure for twisting, etc.